Among the ions $\mathrm{O}^{2-}, \mathrm{Na}^{+}, \mathrm{F}^{-}, \mathrm{N}^{3-}, \mathrm{Mg}^{2+}$ the…
Among the ions $\mathrm{O}^{2-}, \mathrm{Na}^{+}, \mathrm{F}^{-}, \mathrm{N}^{3-}, \mathrm{Mg}^{2+}$ the ions with smallest and largest radii are respectively
$\mathrm{F}^{-}, \mathrm{N}^{3-}$
$\mathrm{Mg}^{2+}, \mathrm{N}^{3-}$
$\mathrm{Na}^{+}, \mathrm{F}^{-}$
$\mathrm{F}^{-}, \mathrm{Na}^{+}$
Solution
The ionic radii of electronic species increases with decrease in magnitude of nuclear charge. Also, the magnitude of nuclear charge decreases with decrease in number of electrons.
When a negative ion is formed by adding one or more electrons, the effective charge is reduced due to which electron-cloud expands and hence atomic radii increases. Therefore, more the negative charge on atom, higher will be the radii. Similarly, more the positive charge on atom, lesser will be the radii.
So, $\mathrm{Mg}^{2+}$ has smallest, while $\mathrm{N}^{3-}$ has largest atomic radii.